diff options
| author | Eric Dumazet <edumazet@google.com> | 2019-12-05 10:10:15 -0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2019-12-06 20:47:38 -0800 |
| commit | 9424e2e7ad93ffffa88f882c9bc5023570904b55 (patch) | |
| tree | 186b56068fd9de539f240ec1ab8cf81fb9ed7a39 | |
| parent | 9a74542eee86313ab7b31ae28b45c59d244e3a85 (diff) | |
| download | lwn-9424e2e7ad93ffffa88f882c9bc5023570904b55.tar.gz lwn-9424e2e7ad93ffffa88f882c9bc5023570904b55.zip | |
tcp: md5: fix potential overestimation of TCP option space
Back in 2008, Adam Langley fixed the corner case of packets for flows
having all of the following options : MD5 TS SACK
Since MD5 needs 20 bytes, and TS needs 12 bytes, no sack block
can be cooked from the remaining 8 bytes.
tcp_established_options() correctly sets opts->num_sack_blocks
to zero, but returns 36 instead of 32.
This means TCP cooks packets with 4 extra bytes at the end
of options, containing unitialized bytes.
Fixes: 33ad798c924b ("tcp: options clean up")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | net/ipv4/tcp_output.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index be6d22b8190f..b184f03d7437 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -755,8 +755,9 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb min_t(unsigned int, eff_sacks, (remaining - TCPOLEN_SACK_BASE_ALIGNED) / TCPOLEN_SACK_PERBLOCK); - size += TCPOLEN_SACK_BASE_ALIGNED + - opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK; + if (likely(opts->num_sack_blocks)) + size += TCPOLEN_SACK_BASE_ALIGNED + + opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK; } return size; |